a. Field of the Invention
The present invention relates to the optical shutter and more particularly, to the flat panel electrostatic display device having a twodimensional array of these shutters; each shutter contains electrically actuated membrane supported by a resilient beam which allows the membrane to move over fixed electrodes on the substrate and thereby modulate transmission and reflection of the incoming light.
b. State of the Prior Art
The electrostatic optical modulator employing a resilient electrode moving over a static electrode has been a subject of many patents and publications. The difference between them originates essentially from the shape of electrodes involved and the direction of movement of the flexible electrode relative to the static one. There are several patents on the electrostatic modulators and displays in which the flexible electrode moves to a curved static electrode thus providing an opening for the light transmission, see e.g. U.S. Pat. No. 4,229,075. Other approaches use an originally curved membrane film which then flattens as the membrane electrostatically moves toward the fixed electrode and thus modulates the light, see e.g. U.S. Pat. Nos. 4,208,103 and 4,786,149.
Various examples of the electrostatic optical shutters are based on the field induced bending of a cantilever membrane which is moved toward a flat static electrode thereby changing the optical state, see U.S. Pat. Nos. 3,553,364, 3,600,798, 4,229,732, 4,731,670 and 5,781,331. Another approach relies on an electrostatically induced twisting of the membrane mirror from its initial flat position to vary the optical reflection, see U.S. Pat. Nos. 3,746,911 and 4,710,732. This electrostatic modulator, known as the Deformable Mirror Device, has been reduced to practice as a commercially available projection display, see e.g. L. J. Hombeck "128.times.128 deformable mirror devices", IEEE Trans.on Electr. Dev., ED-30, p.539,1983, and D. R. Pape and L. J. Hombeck "Characteristics of the deformable mirror device for optical information processing", SPIE 388, p.65, 1983.
Of background interest are also the optical modulators in which electrically actuated membrane displacement changes the conditions of the optical resonance existing between the membrane and the substrate, thus varying the state of optical reflection, see K. W. Goossen et al. "Silicon modulator based on mechanically active antireflection layer with 1 Mbit/sec capability for fiber-on-the-loop applications", IEEE Phot.Techn. Lett. 6,1119,1994; and O. Solgaard et al., "Deformable grating optical modulator", Optics Letters, 17, p.688, 1992.